if param hint is "no hint", then there is no button, so do not update it

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41877 4005530d-fff6-0310-9dd1-cebe43e6787f
Initial implementation of diagram layout unit

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41878 4005530d-fff6-0310-9dd1-cebe43e6787f